Metcalf’s Law Network Utility = Users 2 u How many connections can it make? Ø Ø u 1 user: no utility 100, 000 users: a few contacts 1 million users: many on Net 1 billion users: everyone on Net That is why the Internet is so “hot” Ø Exponential benefit

Transparency in Distributed Systems u Make distributed system as easy to use and manage as a centralized system u Give a Single-System Image u Location transparency: Ø Ø Ø u hide fact that object is remote hide fact that object has moved hide fact that object is partitioned or replicated Name doesn’t change if object is replicated, partitioned or moved. 30

A new programming paradigm u u u Develop object on the desktop Better yet: download them from the Net Script work flows as method invocations All on desktop Then, move work flows and objects to server(s) Gives Ødesktop development Øthree-tier deployment ØSoftware Cyberbricks

Why ACID For Client/Server And Distributed u u u ACID is important for centralized systems Failures in centralized systems are simpler In distributed systems: Ø Ø u More and more-independent failures ACID is harder to implement That makes it even MORE IMPORTANT Ø Ø Simple failure model Simple repair model 81